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If magnetorheological (MR) fluids are stored in porous materials, when excited by the external magnetic field, MR fluid will be drawn out and produce MR effect, which could be used to solve the following problems of the MR damper, such as the seal, volume and the cost of MR fluid damper. In this paper, the effect of structure of metal foams on the performance of MR fluid is investigated; the relationship between the penetrability and the porosity of the metal foams is measured, the change of MR fluid performance flowing though the metal foams is obtained. It shows that, after flowing through metal foams, the change of performance of MR fluid is about 2.5%. Compared to the sponge, the porous metal foams have the obvious advantages in high porosity and rigidity, which provide a convenient and low-cost way to design the MR damper.

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The multiple-step incremental air-bending forming of sheet metal is an important and flexible manufacturing process. It is suitable for sheet parts with complex, curved faces. Most research on incremental air-bending forming are mainly based on experiments and explain the process through macroscopic metal deformation. Based on Hill's yielding criterion and exponential strain hardening law as well as plane strain conditions, an analytical model and ABAQUS finite element model (FEM) are proposed in this article for investigating the incremental air-bending forming process. Firstly, the multiple-step incremental air-bending forming processes on different bending tool parameters are simulated with the FEM to analyze the influences of the tool parameters on formed shape, air-bending forming force, and warpage deformation of the workpiece. Then, the multiple-step incremental air-bending forming process of a semi-ellipse-shaped workpiece with 11 535 mm × 574 mm × 453 mm is simulated with FEM established by the optimum tool parameters as well as the optimal process parameters. Manifested by the experiment for incremental air-bending forming of this workpiece, the numerical simulation method proposed yields satisfactory performance in tool parameters optimization and workpiece forming.

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